/// RFC3016 RTP Payload Format for MPEG-4 Audio/Visual Streams
/// RFC6416 RTP Payload Format for MPEG-4 Audio/Visual Streams
///
/// MPEG-4 Audio streams MUST be formatted LATM (Lowoverhead
/// MPEG-4 Audio Transport Multiplex)[14496 - 3] streams, and the
/// LATM-based streams are then mapped onto RTP packets

#include "rtp-packet.h"
#include "rtp-profile.h"
#include "rtp-payload-internal.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>

struct rtp_encode_mp4a_latm_t {
    struct rtp_packet_t pkt;
    struct rtp_payload_t handler;
    void *cbparam;
    int size;
};

static void *rtp_mp4a_latm_pack_create(int size, uint8_t pt, uint16_t seq, uint32_t ssrc, struct rtp_payload_t *handler,
                                       void *cbparam)
{
    struct rtp_encode_mp4a_latm_t *packer;
    packer = (struct rtp_encode_mp4a_latm_t *)calloc(1, sizeof(*packer));
    if (!packer)
        return NULL;

    memcpy(&packer->handler, handler, sizeof(packer->handler));
    packer->cbparam = cbparam;
    packer->size = size;

    packer->pkt.rtp.v = RTP_VERSION;
    packer->pkt.rtp.pt = pt;
    packer->pkt.rtp.seq = seq;
    packer->pkt.rtp.ssrc = ssrc;
    return packer;
}

static void rtp_mp4a_latm_pack_destroy(void *pack)
{
    struct rtp_encode_mp4a_latm_t *packer;
    packer = (struct rtp_encode_mp4a_latm_t *)pack;
#if defined(_DEBUG) || defined(DEBUG)
    memset(packer, 0xCC, sizeof(*packer));
#endif
    free(packer);
}

static void rtp_mp4a_latm_pack_get_info(void *pack, uint16_t *seq, uint32_t *timestamp)
{
    struct rtp_encode_mp4a_latm_t *packer;
    packer = (struct rtp_encode_mp4a_latm_t *)pack;
    *seq = (uint16_t)packer->pkt.rtp.seq;
    *timestamp = packer->pkt.rtp.timestamp;
}

static int rtp_mp4a_latm_pack_input(void *pack, const void *data, int bytes, uint32_t timestamp)
{
    int r;
    int n, len;
    uint8_t *rtp;
    uint8_t hd[40]; // 10KB
    const uint8_t *ptr;
    struct rtp_encode_mp4a_latm_t *packer;
    packer = (struct rtp_encode_mp4a_latm_t *)pack;
    assert(packer->pkt.rtp.timestamp != timestamp || !packer->pkt.payload /*first packet*/);
    packer->pkt.rtp.timestamp = timestamp; //(uint32_t)(time * KHz); // ms -> 90KHZ (RFC2250 section2 p2)

    r = 0;
    ptr = (const uint8_t *)data;
#if defined(RTP_MP4A_LATM_SKIP_ADTS)
    if (0xFF == ptr[0] && 0xF0 == (ptr[1] & 0xF0) && bytes > 7) {
        // skip ADTS header
        assert(bytes == (((ptr[3] & 0x03) << 11) | (ptr[4] << 3) | ((ptr[5] >> 5) & 0x07)));
        ptr += 7;
        bytes -= 7;
    }
#endif

    // ISO/IEC 14496-3:200X(E)
    // Table 1.44 - Syntax of PayloadLengthInfo() (p84)
    len = bytes / 255 + 1;
    if (len > sizeof(hd)) {
        assert(0);
        return -E2BIG; // invalid packet
    }
    memset(hd, 255, len - 1);
    hd[len - 1] = bytes % 255;

    for (; 0 == r && bytes > 0; ++packer->pkt.rtp.seq) {
        packer->pkt.payload = ptr;
        packer->pkt.payloadlen =
            (bytes + len + RTP_FIXED_HEADER) <= packer->size ? bytes : (packer->size - len - RTP_FIXED_HEADER);
        ptr += packer->pkt.payloadlen;
        bytes -= packer->pkt.payloadlen;

        n = RTP_FIXED_HEADER + len + packer->pkt.payloadlen;
        rtp = (uint8_t *)packer->handler.alloc(packer->cbparam, n);
        if (!rtp)
            return -ENOMEM;

        // Marker (M) bit: The marker bit indicates audioMuxElement boundaries.
        // It is set to 1 to indicate that the RTP packet contains a complete
        // audioMuxElement or the last fragment of an audioMuxElement.
        packer->pkt.rtp.m = (0 == bytes) ? 1 : 0;
        n = rtp_packet_serialize_header(&packer->pkt, rtp, n);
        if (n != RTP_FIXED_HEADER) {
            assert(0);
            return -1;
        }

        if (len > 0)
            memcpy(rtp + n, hd, len);
        memcpy(rtp + n + len, packer->pkt.payload, packer->pkt.payloadlen);
        r = packer->handler.packet(packer->cbparam, rtp, n + len + packer->pkt.payloadlen, packer->pkt.rtp.timestamp,
                                   0);
        packer->handler.free(packer->cbparam, rtp);
        len = 0; // write PayloadLengthInfo once only
    }

    return r;
}

struct rtp_payload_encode_t *rtp_mp4a_latm_encode()
{
    static struct rtp_payload_encode_t encode = {
        rtp_mp4a_latm_pack_create,
        rtp_mp4a_latm_pack_destroy,
        rtp_mp4a_latm_pack_get_info,
        rtp_mp4a_latm_pack_input,
    };

    return &encode;
}
